gThumb, an image viewer and organizer for the GNOME environment, was released in version 3.11.3 a few days ago. A significant change in this version is the addition of the JPEG XL format (.jxl). The JPEG XL format builds upon Google's Pik format and Cloudinary's FUIF format. The JPEG Committee developed the codec as the next generation of image compression.
gThumb is an image viewer and browser written for the GNOME environment. It allows you to browse your hard drive and view thumbnail images of image files and individual pictures of various formats. Graphic formats supported by gThumb include JPEG, GIF, TIF, and PNG. gThumb can display other image types, including TGA, ICO, BMP, XPM, and others if the supporting libraries are installed. If you have the dcraw program installed on your computer, you will support RAW image types. gThumb not only allows you to view image files but has several other valuable features such as the ability to add comments to images, organize images into catalogs, print images, create slideshows, set your desktop background, and more. GThumb includes a feature for importing photos from attached cameras and memory card readers. Many metadata formats such as EXIF, XMP, and IPTC can be read by gThumb. gThumb offers a system of extensions (or plug-ins) that can be used to extend its functionality.
GThumb has supported JPEG XL since version 3.11.3. Ensure that this version is installed and that you can read and write JPEG XL files as you would any other image.